#48 how would i do this? i don't believe my answer is right

Well you have to make the powers line up so we know r^4 is the highest and you work your way down so

0r^4-5r^3-4r^2-3r
R^4+0r^3-4r^2+3r

So now that they are lined up by power we solve (keep in mind that the 0r's are place holders and have no value)

R^4-5r^3-8r^2

That's your answer